1. Field of the Invention
The present invention relates to a plant controller.
2. Discussion of the Background
Japanese Unexamined Patent Application Publication No. 2001-90584 discloses an air-fuel ratio controller of an internal combustion engine. Such a controller performs feedback control based on the deviation between a detected air-fuel ratio and a target air-fuel ratio and thereby determines an air-fuel ratio correction coefficient. More specifically, the air-fuel ratio correction coefficient is calculated by a model defining equation that defines a model to be subjected to control, and a control parameter that is a coefficient of the model defining equation is calculated on the basis of the amount of engine intake air, the response time constant of an air-fuel sensor, and a calculation interval. Then, the air-fuel ratio correction coefficient is determined by applying the thus calculated control parameter to the model defining equation.
The conventional controller described above determines the air-fuel ratio correction coefficient that is a control input using a control parameter to be set on the basis of the amount of engine intake air. The calculation of such a control parameter uses a control gain ω that is set in advance by taking into consideration the control stability and response.